1. Field of the Invention
The present invention relates to an optical disc system in which a compact disc (CD) and a digital video disc (DVD) can be compatibly used, and more particularly, to a method and apparatus for discriminating between a CD and a DVD by detecting a reflection signal from a surface area of the optical disc and a focusing signal from a recording area thereof.
2. Description of the Related Art
A digital video disc (DVD) is a more recently developed optical disc and is capable of recording more information than a conventional compact disc (CD). In comparison with the CD, the DVD has a higher recording density, and accordingly, a shorter distance between a surface area and a recording area. Practically, a distance between the surface area and the recording area of a DVD is 0.6 mm while that of a CD is 1.2 mm. Therefore, in order to perform adequate servo operations, an optical disc system must first determine whether an optical disc inserted therein is the CD or the DVD.
A conventional method for discriminating between the CD and the DVD will be described with reference to FIG. 1. When the optical disc is inserted, a reflection signal 110 is detected from the surface area of the optical disc, and a reflection signal detection time is stored. Thereafter, an S-curve signal 120 is detected from the recording area of the optical disc, and an S-curve signal detection time is stored. It is noted that the S-curve signal is a focusing signal generated by scanning an optical beam onto the recording area of the disc. Thereafter, a time difference between the reflection signal detection time and the S-curve signal detection time is calculated, and the calculated time difference is stored as a disc detection time 130. If the time difference between the reflection signal detection time and the S-curve signal detection time, i.e., the disc detection time 130, is above a predetermined reference time, the inserted disc is determined to be the CD, and if not, the DVD.
However, due to a difference in DC sensitivity of a pickup, a non-linear characteristic of an actuator, and, in the case of a special disc like a non-circular disc, a position and a direction of the optical disc placed in a tray, there may be a deviation in the disc detection time 130. Further, due to the difference in the DC sensitivity of the pickup and the non-linear characteristic of the actuator, the predetermined reference time used to discriminate between the CD and the DVD may be different from one optical disc system to another. Therefore, the conventional method occasionally causes an error in discriminating between the CD and the DVD.